A permanent magnet brushless DC motor usually comprises a shaft, a rotor core fixed to the shaft and one or more magnets disposed around the core. In the prior art, the magnet and the rotor core are usually attached by a binder such as an epoxy resin. The binder is used as a torque transfer structure between the magnet and the rotor core for transferring the rotational torque of the magnet to the shaft, thereby driving the shaft.
However, adhesion by means of a binder has following disadvantages:
1) With changes in temperature and prolongation of the duration of usage, the binder is easily aged and may lose its adhesive strength, thereby resulting in failure of the rotor.
2) The manufacturability is poor. A paste binder is difficult to apply evenly, in production which easily results in the magnet being eccentrically mounted to the rotor core, thereby generating one extra factor affecting the imbalance of the rotor.
Hence, it is desirable to develop a new torque transfer structure between the magnet and the core.